ReactJS.NET includes an MSBuild task for compiling JSX into JavaScript. This is handy to improve the start time of your application, especially if you have a large number of JSX files.

To use it, first reference the TransformBabel task, and then call it wherever you like:

<Target Name="TransformBabel">
    <TransformBabel SourceDir="$(MSBuildProjectDirectory)" TargetDir="" />

To get started easily, you can install the React.MSBuild NuGet package which will automatically modify your web application's .csproj file to reference the task and run it after every site compilation. To customise the process (for example, to only compile the JSX files for release builds), modify the TransformBabel build target that was added to the csproj file.

The NuGet package is good for getting started quickly, but it has some limitations. The package needs to add a reference to React.MSBuild.dll, even though this assembly is only used at build time and not actually used at runtime. Instead of using the NuGet package, you can just manually copy all the assembly files into a folder (such as tools\React) and just reference the task manually.